qemu: Move CPU validation out of PostParse

qemu: Move CPU validation out of PostParse

The qemuDomainDefCPUPostParse() does a bit more than filling in
missing info. It also validates CPU cache configuration. Move
that code into qemuValidateDomainDefCpu() where the code fits
better.

And since I need to fix indentation of existing code in
qemuValidateDomainDefCpu(), I'm taking this opportunity and move
error messages onto single line. Interestingly, this uncovers a
bug we have in sc_prohibit_diagnostic_without_format syntax-check
rule, because previously a virReportError() with a message
spawned over three lines was not caught but not it is. But
trying to understand that regex is a job for another time.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>